The KV tanks were a series of Soviet heavy tanks named after the Soviet defense commissar and politician Kliment Voroshilov and used by the Red Army during World War II. The KV series were known for their extremely heavy armour protection during the early part of the war, especially during the first year of the German invasion of the Soviet Union. They were practically immune to the 3.7 cm KwK 36 and howitzer-like, short barreled 7.5 cm KwK 37 guns mounted, respectively, on the early Panzer III and Panzer IV tanks fielded by the invading German forces. Until more effective guns were developed by the Germans, the KV-1 was invulnerable to almost any German weapon except the 8.8 cm Flak gun. Even then, the sloped and reinforced front armor and turret of the KV-1 caused some hits from the 8.8 cm Flak gun to ricochet.

Designed to replace the disappointing multi-turreted T-35 heavy tank, the Soviet KV was in service from 1939 to 1945. The primary goal of the KV's designers was to build a tank with impenetrable armor, and they succeeded—any tank in service at the time of the KV's introduction would have had to attack at point blank range in order to breach its hull. It also had good firepower and traction, but was unfortunately slow and difficult to steer. By 1942, with the introduction of 50 and 75 mm guns and the high-velocity MK 10, the KV had lost its armor advantage, though it remained in service through the end of the war.